1. Technical Field
The present invention relates to a magnetic head structure that is obtained by forming a medium facing surface of a head element unit by polishing processing, and its manufacturing method.
2. Description of the Related Art
When a magnetic head is manufactured, generally a bar-like magnetic head substrate, in which a plurality of head element units are arranged in a row or an individual (chip-like) magnetic head in which one head element unit is formed on a wafer, is obtained by arranging head element units, in which at least a reproducing element and a recording element are laminated, in plural rows on one wafer (substrate), then cutting the wafer in individual rows, and forming a surface (medium facing surface) facing a recording medium by polishing processing.
The height of a head element unit is also simultaneously specified by the polishing processing for forming the above medium facing surface. The height of the head element unit is specifically the height of a reproducing element, the gap length of a magnetic gap layer of a recording element if a longitudinal recording method is adopted, and the neck height of a main magnetic pole layer of a recording element if a vertical recording method is adopted. Since these are important factors that contribute to reproducing characteristics or recording characteristic, it is desirable that they are specified correctly.
Thus, in the related art, a method of carrying out the above polishing processing using a height monitor, and detecting the height of the head element unit from the width (dimension in a track width direction) of the height monitor exposed to a polishing processing surface is suggested. One pair of the height monitors is provided on both sides of a head element unit in the track width direction, and are formed in the same process in the same laminating height position as a layer of the head element unit to be monitored, using photolithography. Generally, the pair of height monitors forms a triangular or trapezoidal planar shape, and is arranged in directions (symmetrical shape) opposite to each other in the height direction. The width of the height monitors exposed to the polishing processing surface is infinitesimal with respect to the height of the head element unit, and is measured by a length-measuring SEM (CD-SEM).
However, if one tries to form triangular or trapezoidal height monitors, acute portions cannot be easily exposed by the proximity effect of light during resist exposure. Therefore, corners are rounded, and consequently, the desired shapes cannot be obtained. In the monitors including curved portions as such, the linearity (correlativity) of the width of the monitors exposed to the polishing processing surface and the height of the head element unit is worsened, and it is difficult to detect the height of the head element unit with high precision. In order to avoid this problem, it is conceivable to enlarge the planar shape of the height monitors to use portions excluding the curved portions as the monitors during polishing processing. However, if the planar shape of the height monitor is simply enlarged, the width of the monitors exposed to the polishing processing surface is not converged into the viewing field region of the length-measuring SEM, and consequently, the resolution of SEM cannot help being lowered. If the resolution of SEM is lowered, the measurement precision of the monitor width will decline, and errors in the height of the head element unit calculated on the basis of the monitor width will increase. Consequently, even in this case, it is difficult to detect the height of the head element unit with high precision.
JP-A-4-78013 (Patent Document 1) discloses a detecting marker that is formed in a polygonal shape by cutting away the apexes of a triangle so that acute portions that are easily deformed may not exist in is Patent Document 1. However, the angles of respective corners in such a polygonal shape are different from one another. Therefore, if a pair of monitors is provided on both side of the head element unit, their symmetric property is hardly obtained, and regions that can be effectively used as the monitors may be narrowed.